JP6180681B1 - Non-aqueous electrolyte secondary battery negative electrode carbonaceous material and method for producing the same - Google Patents

Abstract

An object of the present invention is to provide a non-aqueous electrolyte secondary battery having high discharge capacity and high charge / discharge efficiency. The subject is a carbonaceous material using the plant of the present invention as a carbon source, the potassium element content is 0.10% by weight or less, and the true density required by the butanol method is 1.35 to 1.50 g / When the carbonaceous material is electrochemically doped with lithium and the NMR spectrum of the lithium nucleus is measured, the main material is shifted to the low magnetic field side by 110 to 160 ppm with respect to the resonance peak of LiCl as the reference material. This can be solved by a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery characterized by exhibiting a resonance peak.

Description

  The present invention relates to a carbonaceous material for a non-aqueous electrolyte secondary battery. ADVANTAGE OF THE INVENTION According to this invention, the negative electrode carbonaceous material for nonaqueous electrolyte secondary batteries which has high discharge capacity and shows the outstanding charging / discharging efficiency can be provided.

  In recent years, due to increasing interest in environmental problems, large secondary batteries with high energy density and excellent output characteristics are being installed in electric vehicles. Particularly in EV applications, further increase in energy density is expected in order to extend the cruising distance by one charge. The theoretical capacity of the graphite material currently used mainly for storing lithium is 372 Ah / kg, which is theoretically limited. In addition, alloy-based negative electrode materials such as tin and silicon have also been proposed as materials having a high capacity, but these are not sufficiently durable due to large expansion / contraction due to charge / discharge, and are added to graphite for several percent. Use is limited, such as using. In contrast, amorphous carbon materials are expected to be high-capacity negative electrode materials because they are excellent in durability and have a high capacity that exceeds the theoretical capacity of graphite materials that can store lithium in terms of weight. However, the carbon materials reported so far have not had a sufficient capacity.

JP-A-8-64207 JP 2008-10337 A Japanese Patent Laid-Open No. 9-7598

  An object of the present invention is to provide a non-aqueous electrolyte secondary battery having high discharge capacity and high charge / discharge efficiency. Furthermore, the objective of this invention is providing the negative electrode carbon material for secondary batteries used for the said battery.

As a result of intensive research on a nonaqueous electrolyte secondary battery having a high discharge capacity and a high charge / discharge efficiency, the present inventor has surprisingly been a reference substance when an NMR spectrum of lithium nuclei is measured. It has been found that a nonaqueous electrolyte secondary battery using a carbonaceous material having a main resonance peak shifted by 110 to 160 ppm on the low magnetic field side with respect to the resonance peak of LiCl exhibits excellent discharge capacity and charge / discharge efficiency.
The present invention is based on these findings.
Therefore, the present invention
[1] A carbonaceous material having a plant as a carbon source, having a potassium element content of 0.10% by weight or less, and a true density required by a butanol method of 1.35 to 1.50 g / cm ³ . When the carbonaceous material is electrochemically doped with lithium and the NMR spectrum of the lithium nucleus is measured, the main resonance peak shifted by 110 to 160 ppm toward the low magnetic field side with respect to the resonance peak of LiCl as the reference substance A carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery,
[2] The press specific surface area ratio (A / B) of the specific surface area (A) determined by the BET method when the carbonaceous material is pressed at 2.6 MPa and the specific surface area (B) before pressing is 10 or less. The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to [1],
[3] The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to [1] or [2], wherein the ratio of hydrogen atoms to carbon atoms determined by elemental analysis is 0.10 or less.
[4] For a negative electrode of a nonaqueous electrolyte secondary battery according to any one of [1] to [3], wherein a true density measured using helium as a substitution medium is 1.30 to 2.00 g / cm ³ . Carbonaceous materials,
[5] The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to any one of [1] to [4], wherein the true density determined by the butanol method is 1.35 to 1.46 g / cm ³ .
[6] The nonaqueous electrolyte according to any one of [1] to [5], which is obtained from an alkali-treated carbonaceous precursor that is heat-treated at 500 ° C. to 1000 ° C. in a non-oxidizing gas atmosphere. Carbonaceous material for secondary battery negative electrode,
[7] A negative electrode for a nonaqueous electrolyte secondary battery comprising the carbonaceous material according to any one of [1] to [6],
[8] The negative electrode for a nonaqueous electrolyte secondary battery according to [7], wherein the electrode density is 0.80 g / cm ³ or more,
[9] A nonaqueous electrolyte secondary battery having the negative electrode according to [7] or [8],
[10] (1) An alkali-adding step of adding a compound containing an alkali metal element to plant-derived char to obtain an alkali-attached plant-derived char; (2) the alkali-attached plant-derived char in a non-oxidizing gas atmosphere Heat treatment step of obtaining an alkali-treated carbonaceous precursor by heat treatment at 500 ° C to 1000 ° C in (3), wherein the alkali-treated carbonaceous precursor is heated at 500 ° C to 1250 ° C in an inert gas atmosphere containing a halogen compound. Gas phase decalcification step for heat treatment (4) Step of pulverizing the carbonaceous precursor obtained by gas phase decalcification, (5) 800 to 1600 ° C. of the pulverized carbonaceous precursor in a non-oxidizing gas atmosphere And (6) a method for producing a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery, comprising the step of: (6) coating the fired product with pyrolytic carbon.
[11] The main firing step (5) and the coating step (6) are volatile at a room temperature when the carbonaceous precursor is pulverized and the residual carbon ratio is less than 5% by weight when ignited at 800 ° C. The method for producing a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery according to [10], wherein the organic compound is mixed, and the main calcination is performed at 800 ° C. to 1600 ° C. in a non-oxidizing gas atmosphere.
[12] (7) The method for producing a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery according to [10] or [11], further comprising a step of heat treatment at 800 ° C. to 1500 ° C. in a non-oxidizing gas atmosphere. [13] The method for producing a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery according to any one of [10] to [12], wherein the alkali-attached amount of the alkali-derived plant-derived char is 5% by weight or more. ,
About.
In addition, the carbonaceous material which has the main resonance peak shifted 80-200 ppm to the low magnetic field side with respect to the resonance peak of the reference material LiCl is described in the claims of Patent Document 1. However, the carbonaceous material using the coconut shell obtained in the examples as a carbon source is a carbonaceous material having a main resonance peak shifted by 105 ppm. In addition, the carbonaceous material having a resonance peak shifted by 10 to 40 ppm and a resonance peak shifted by 55 to 130 ppm is disclosed in the claims of Patent Document 2. However, the carbonaceous material obtained in the examples is a carbonaceous material having a resonance peak shifted by about 90 ppm and a resonance peak shifted by 20 ppm. Furthermore, the claim of patent document 3 describes a carbon material having peaks at 10 to 20 ppm and 110 to 140 ppm when an NMR spectrum of lithium nuclei is measured at −40 ° C. However, this NMR spectrum was measured at −40 ° C., and the carbonaceous materials described in the examples are based on pitch as a carbon source.
Therefore, as far as the present inventor knows, in the carbonaceous material using plants as a carbon source, a carbonaceous material having a main resonance peak shifted by 110 to 160 ppm on the low magnetic field side with respect to the resonance peak of LiCl has been obtained. There wasn't.

  According to the carbonaceous material for a non-aqueous electrolyte secondary battery of the present invention, a non-aqueous electrolyte secondary battery having a high discharge capacity and excellent charge / discharge efficiency can be produced. A carbonaceous material having a main resonance peak shifted by 110 to 160 ppm has a low irreversible capacity, and thus is considered to exhibit a high discharge capacity and excellent charge / discharge efficiency. That is, the carbonaceous material of the present invention is considered to have optimum pores into which lithium that can be doped and dedoped is inserted.

[1] Non-aqueous electrolyte secondary battery negative electrode carbonaceous material The non-aqueous electrolyte secondary battery negative electrode carbonaceous material of the present invention is a carbonaceous material using plants as a carbon source and has a potassium element content of 0. 10% by weight or less, the true density required by the butanol method is 1.35 to 1.50 g / cm ³ , the carbonaceous material is electrochemically doped with lithium, and the NMR spectrum of the lithium nucleus is measured. In this case, the main resonance peak shifted by 110 to 160 ppm toward the low magnetic field side with respect to the resonance peak of LiCl as the reference substance is shown.
The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode of the present invention is not limited, but can be produced by the “method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode” described later. That is, it can be produced by (1) an alkali deposition step, (2) a heat treatment step, (3) a vapor phase decalcification step, (4) a pulverization step, (5) a main firing step, and (6) a coating step. is there. In particular, (2) the carbonaceous material having the butanol true density is obtained by a heat treatment step in which the alkali-derived plant-derived char is heat-treated at 500 ° C. to 1000 ° C. in a non-oxidizing gas atmosphere to obtain an alkali-treated carbonaceous precursor. Material can be obtained.

《Carbon source》
The carbon source of the carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode of the present invention is derived from a plant. The carbon source plant is not particularly limited, and examples thereof include coconut husks, coffee beans, tea leaves, sugar cane, fruits (mandarin oranges or bananas), persimmons, hardwoods, conifers, bamboo, or rice husks. it can. These plants can be used singly or in combination of two or more kinds, but particularly coconut shells or coffee beans are preferred because they are available in large quantities.
The coconut as a raw material for the coconut shell is not particularly limited, and examples thereof include palm palm (oil palm), coconut palm, salak, and coconut palm. Coconut shells obtained from these palms can be used alone or in combination, but they are used as foods, detergent raw materials, biodiesel oil raw materials, etc. A shell is particularly preferred.
The carbon source using the coffee beans is preferably an extraction residue obtained by extracting beverage coffee components from coffee beans. The extraction residue is partly extracted and removed when extracting the coffee components. Among them, the industrially extracted coffee extraction residue is moderately crushed and available in large quantities. Is particularly preferred.
Plant-derived carbon sources have voids derived from conduits and phloem pipes, so that an optimum pore structure is formed by heat treatment after alkali addition, excellent discharge capacity, and excellent charge / discharge It can be used as a negative electrode material for secondary batteries exhibiting efficiency.

<Potassium element content>
The potassium element content of the carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery of the present invention is 0.10% by weight or less, preferably 0.05% by weight or less, more preferably 0.03% by weight or less. is there. In a non-aqueous electrolyte secondary battery using a carbon material for a negative electrode having a potassium content exceeding 0.10% by weight, the dedoping capacity may decrease and the undoping capacity may increase.

《True density》
The true density of the graphite material having an ideal structure is 2.27 g / cm ³ , and the true density tends to decrease as the crystal structure is disturbed. Therefore, the true density can be used as an index representing the structure of carbon.

《Butanol true density》
The butanol true density of the carbonaceous material of the present invention is 1.35 to 1.50 g / cm ³ . The upper limit of the true density is preferably 1.48 g / cm ³ or less, more preferably 1.46 g / cm ³ or less, and most preferably 1.45 g / cm ³ or less. The lower limit of the true density is preferably 1.36 g / cm ³ or more, more preferably 1.37 g / cm ³ or more, still more preferably 1.38 g / cm ³ or more, and most preferably 1.39 g. / Cm ³ or more. A carbonaceous material having a true density exceeding 1.50 g / cm ³ has few pores of a size capable of storing lithium and may have a small doping and dedoping capacity. Further, since the increase in true density is accompanied by selective orientation of the carbon hexagonal plane, it is not preferable because the carbonaceous material often involves expansion and contraction during lithium doping and dedoping. On the other hand, a carbonaceous material of less than 1.35 g / cm ³ may not be able to maintain a stable structure as a lithium storage site because the electrolyte solution penetrates into the pores. Furthermore, since the electrode density is lowered, the volume energy density may be lowered.

《Helium true density》
The true density (ρ _He ) measured using helium gas as a replacement medium is an indicator of helium gas diffusivity, and this value is large and shows a value close to the theoretical density of carbon 2.27 g / cm ^3. This means that there are many pores that can be formed. In other words, it means that there are abundant holes. On the other hand, since helium has a very small atomic diameter (0.26 nm), it can be considered that pores smaller than the helium atomic diameter are closed, and low helium gas diffusivity means that there are many closed holes. Means that.
Although the negative electrode material for nonaqueous electrolyte secondary batteries of this invention is not limited, it is 1.35-2.00 g / cm < ³ >. The lower limit of the helium true density is preferably 1.36 g / cm ³ or more, and more preferably 1.37 g / cm ³ or more. The upper limit of the helium true density is preferably 1.90 g / cm ³ or less, more preferably 1.80 g / cm ³ or less. A carbonaceous material having a helium true density of less than 1.35 g / cm ³ may fill the pores and reduce the discharge capacity. In addition, a carbonaceous material having a helium true density exceeding 2.00 g / cm ³ may not have a sufficient carbonaceous film to increase the irreversible capacity. That is, it is considered that the efficiency of the secondary battery is improved when the helium true density is in the above range.

<< NMR spectrum of lithium nucleus >>
The carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery of the present invention has a low magnetic field side with respect to the resonance peak of LiCl, which is a reference substance, when electrochemically doped with lithium and the NMR spectrum of a lithium nucleus is measured. Shows the main resonance peak shifted by 110 to 160 ppm. In the present specification, the “main resonance peak” means a peak having the maximum peak area among resonance peaks in the range of 0 ppm to 160 ppm on the low magnetic field side.

  The lower limit of the main resonance peak of the carbonaceous material for a non-aqueous electrolyte secondary battery negative electrode of the present invention is preferably 113 ppm, more preferably 116 ppm, still more preferably 120 ppm, and most preferably 124 ppm. When the main resonance peak is less than 110 ppm, a sufficient discharge capacity may not be obtained. The upper limit of the main resonance peak is preferably 155 ppm, more preferably 150 ppm. When the main resonance peak exceeds 160 ppm, the press resistance may decrease.

  The main resonance peak is shifted to the low magnetic field side by 110 to 160 ppm with respect to the resonance peak of LiCl, so that the nonaqueous electrolyte secondary battery using the carbonaceous material of the present invention has an excellent discharge capacity and an excellent discharge capacity. The charging / discharging efficiency can be shown. The carbonaceous material for the negative electrode of the non-aqueous electrolyte secondary battery of the present invention is not limited, but is alkali-attached to plant-derived char, heat-treated at 500 ° C. to 1000 ° C., and gas phase deashed. It can obtain by using the carbonaceous precursor obtained by this.

The main resonance peak was measured by repeating the operation of energizing for 1 hour at a current density of 0.50 mA / cm ² and then resting for 2 hours until the equilibrium potential between the terminals reached 4 mV. Positive electrode). After completion of the doping, the carbon electrode (positive electrode) is taken out in an argon atmosphere, the electrode surface is washed with dimethyl carbonate, dried, and then used for NMR spectrum measurement. The amount of the carbonaceous material in the positive electrode used for the measurement was adjusted to 40 mg (20 mg × 2 sheets). The secondary battery is a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (1: 2: 2) containing LiPF ₆ (1.4 mol / liter) as a carbon electrode (positive electrode), a lithium negative electrode, and an electrolytic solution. Can be used. Further, the carbon electrode (positive electrode) was made into a paste by adding N-methyl-2-pyrrolidone to 90 parts by weight of the carbonaceous material powder and 10 parts by weight of polyvinylidene fluoride (“KF # 1100” manufactured by Kureha Co., Ltd.) After uniformly coating on the copper foil and drying, a material punched into a disk shape having a diameter of 15 mm can be used. The negative electrode can be a metal lithium thin plate having a thickness of 0.8 mm punched into a disk shape having a diameter of 15 mm.
The measurement temperature of the main resonance peak is not particularly limited, but is preferably room temperature, for example, 20 to 30 ° C, preferably 25 to 30 ° C, and more preferably 26 ° C. By measuring at room temperature, several peaks do not appear and measurement of the main resonance peak is facilitated.

"Specific surface area"
The specific surface area can be obtained by an approximate expression derived from the BET expression by nitrogen adsorption. The specific surface area of the carbonaceous material of the present invention is 30 m ² / g or less. When the specific surface area exceeds 30 m ² / g, the reaction with the electrolytic solution increases, leading to an increase in irreversible capacity, and thus battery performance may be reduced. The upper limit of the specific surface area is preferably 30 m ² / g or less, more preferably 20 m ² / g or less, and particularly preferably 10 m ² / g or less. Further, the lower limit of the specific surface area is not particularly limited, but if the specific surface area is less than 0.5 m ² / g, the input / output characteristics may be lowered, so the lower limit of the specific surface area is preferably 0.5 m. ² / g or more.

《Press specific surface area ratio》
The carbonaceous material for a non-aqueous electrolyte secondary battery negative electrode of the present invention is a ratio before and after pressing between the specific surface area (A) determined by the BET method when pressed at 2.6 MPa and the specific surface area (B) before pressing. The surface area ratio (A / B) (hereinafter referred to as the press specific surface area ratio) is 10 or less. The press specific surface area ratio is preferably 10 or less, more preferably 8 or less, and still more preferably 6 or less. The lower limit of the press specific surface area ratio is 1, but may be 1.1 or more in one aspect, 1.2 or more in another aspect, and 1.3 or more in another aspect.
The non-aqueous electrolyte secondary battery negative electrode carbonaceous material of the present invention has excellent press resistance. Specifically, the structure of the carbonaceous material is not easily destroyed with respect to the pressure during the production of the carbon electrode (positive electrode). When the structure of the carbonaceous material is destroyed, an increase in the specific surface area is observed, but the carbonaceous material of the present invention has excellent press resistance, so that the specific surface area increases even when a strong pressure is applied. Few. The press specific surface area ratio indicates press resistance, and the closer the value is to 1, the better press resistance is.

  The reason why the carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery of the present invention has excellent press resistance has not been analyzed in detail, but can be considered as follows. However, the present invention is not limited by the following description. The carbonaceous material of the present invention uses a plant-derived carbon source. Furthermore, the carbonaceous material of the present invention is produced using a carbonaceous precursor obtained by alkali-impregnating plant-derived char, heat-treating it from 500 ° C. to 1000 ° C., and performing vapor phase deashing. The The carbonaceous material obtained from the carbonaceous precursor has an appropriate amount of pores and can maintain good press resistance because the carbon skeleton has sufficient toughness.

The pressing at 2.6 MPa can be performed by the following method. A carbonaceous material (0.5 g) is filled into a cylindrical mold having a diameter of 10 mm and pressed at 2.6 MPa (1 tf / cm ² ). The pressed carbonaceous material was measured for the specific surface area using the method described in the Examples, and calculated as the specific surface area (A) determined by the BET method.

<< Atomic ratio of hydrogen atom to carbon atom (H / C) >>
H / C is measured by elemental analysis of hydrogen atoms and carbon atoms. Since the hydrogen content of the carbonaceous material decreases as the degree of carbonization increases, H / C tends to decrease. Therefore, H / C is effective as an index representing the degree of carbonization. H / C of the carbonaceous material of the present invention is 0.10 or less, more preferably 0.08 or less. Especially preferably, it is 0.05 or less. When the ratio H / C of hydrogen atoms to carbon atoms exceeds 0.10, there are many functional groups in the carbonaceous material, and the lithium doped into the negative electrode carbon by reaction with lithium is not completely dedope, There is a problem that a large amount of lithium remains in the negative electrode carbon, and lithium as an active material is wasted.

_<< Average particle diameter _Dv50 >>
The average particle diameter (D _v50 ) of the carbonaceous material of the present invention is 1 to 50 μm. The lower limit of the average particle diameter is preferably 1 μm or more, more preferably 1.5 μm or more, and particularly preferably 2.0 μm or more. When the average particle diameter is less than 1 μm, the specific surface area is increased by increasing the fine powder. Therefore, the irreversible capacity, which is a capacity that does not discharge even when charged due to increased reactivity with the electrolytic solution, is increased, and the proportion of wasted capacity of the positive electrode is increased. The upper limit of the average particle diameter is preferably 40 μm or less, more preferably 35 μm or less. When the average particle diameter exceeds 50 μm, the lithium free diffusion process in the particles increases, so that rapid charge / discharge becomes difficult. Further, in the secondary battery, it is important to increase the electrode area in order to improve the input / output characteristics. For this reason, it is necessary to reduce the coating thickness of the active material on the current collector plate during electrode preparation. In order to reduce the coating thickness, it is necessary to reduce the particle diameter of the active material. From such a viewpoint, the upper limit of the average particle diameter is preferably 50 μm or less.

[2] Negative electrode for non-aqueous electrolyte secondary battery << Manufacture of negative electrode >>
In the negative electrode using the carbonaceous material of the present invention, a binder (binder) is added to the carbonaceous material, and an appropriate solvent is added and kneaded to form an electrode mixture. It can be produced by pressure molding after coating and drying. By using the carbonaceous material of the present invention, it is possible to produce an electrode having high conductivity without adding a conductive auxiliary agent. When preparing the agent, a conductive aid can be added. As the conductive auxiliary agent, acetylene black, ketjen black, carbon nanofiber, carbon nanotube, carbon fiber or the like can be used, and the addition amount varies depending on the type of conductive auxiliary agent used, but the added amount is small. If the amount is too large, the expected conductivity cannot be obtained, and this is not preferable. If the amount is too large, the dispersion in the electrode mixture deteriorates. From such a viewpoint, the preferable ratio of the conductive auxiliary agent to be added is 0.5 to 15% by weight (where the amount of the active material (carbonaceous material) + the binder amount + the conductive auxiliary agent amount = 100% by weight). More preferably 0.5 to 7% by weight, particularly preferably 0.5 to 5% by weight. The binder is not particularly limited as long as it does not react with an electrolytic solution such as PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and a mixture of SBR (styrene-butadiene rubber) and CMC (carboxymethylcellulose). Among them, PVDF is preferable because PVDF attached to the surface of the active material hardly inhibits lithium ion migration and obtains favorable input / output characteristics. In order to dissolve PVDF and form a slurry, a polar solvent such as N-methylpyrrolidone (NMP) is preferably used, but an aqueous emulsion such as SBR or CMC can also be used by dissolving in water. When the amount of the binder added is too large, the resistance of the obtained electrode is increased, which is not preferable because the internal resistance of the battery is increased and the battery characteristics are deteriorated. Moreover, when there is too little addition amount of a binder, the coupling | bonding with negative electrode material particle | grains and a collector is insufficient, and it is unpreferable. Although the preferable addition amount of a binder changes also with kinds of binder to be used, it is preferably 3 to 13% by weight, more preferably 3 to 10% by weight in the case of a PVDF type binder. On the other hand, in a binder using water as a solvent, a mixture of a plurality of binders such as a mixture of SBR and CMC is often used, and the total amount of all binders used is preferably 0.5 to 5% by weight. Preferably it is 1-4 weight%. The electrode active material layer is basically formed on both sides of the current collector plate, but may be on one side if necessary. A thicker electrode active material layer is preferable for increasing the capacity because fewer current collector plates and separators are required. However, the larger the electrode area facing the counter electrode, the better the input / output characteristics, and the thicker the active material layer. Too much is not preferable because the input / output characteristics deteriorate. The thickness of a preferable active material layer (per one side) is not limited, and may be within a range of 10 μm to 1000 μm in consideration of various uses. However, it is preferably 10 to 200 μm, more preferably 10 to 150 μm, still more preferably 20 to 120 μm, and particularly preferably 30 to 100 μm.
The negative electrode usually has a current collector. As the negative electrode current collector, for example, SUS, copper, nickel, or carbon can be used, and among them, copper or SUS is preferable.

[3] Nonaqueous electrolyte secondary battery When the negative electrode material of the present invention is used to form the negative electrode of a nonaqueous electrolyte secondary battery, other materials constituting the battery, such as a positive electrode material, a separator, and an electrolytic solution, are not particularly limited. It is possible to use various materials conventionally used or proposed as a nonaqueous solvent secondary battery.

(Positive electrode)
The positive electrode includes a positive electrode active material, and may further include a conductive additive, a binder, or both. The mixing ratio of the positive electrode active material and other materials in the positive electrode active material layer is not limited as long as the effect of the present invention is obtained, and can be determined as appropriate.
The positive electrode active material can be used without limiting the positive electrode active material. For example, a layered oxide system (expressed as LiMO ₂ , where M is a metal: for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , or LiNi _x Co _y Mn _z O ₂ (where x, y, z are composition ratios) ), Olivine-based (represented by LiMPO ₄ , M is a metal: for example LiFePO ₄ ), spinel-based (represented by LiM ₂ O ₄ , M is a metal: for example LiMn ₂ O ₄ ) Compounds may be mentioned, and these chalcogen compounds may be mixed as necessary.
In addition, a ternary system [Li (Ni-Mn-Co) in which a part of cobalt of lithium cobaltate is replaced with nickel and manganese, and the stability of the material is improved by using three of cobalt, nickel, and manganese. NCA-based materials [Li (Ni—Co—Al) O ₂ ] using aluminum instead of O ₂ ] and the ternary manganese are known, and these materials can be used.

The positive electrode can further contain a conductive additive and / or a binder. As a conductive support agent, acetylene black, ketjen black, or carbon fiber can be mentioned, for example. Although content of a conductive support agent is not limited, For example, it is 0.5 to 15 weight%. Moreover, as a binder, fluorine-containing binders, such as PTFE or PVDF, can be mentioned, for example. Although content of a conductive support agent is not limited, For example, it is 0.5 to 15 weight%. Further, the thickness of the positive electrode active material layer is not limited, but may be within a range of 10 μm to 1000 μm in consideration of various uses. However, it is preferably 10 to 200 μm, more preferably 10 to 150 μm, still more preferably 20 to 120 μm, and particularly preferably 30 to 100 μm.
The positive electrode active material layer usually has a current collector. As the negative electrode current collector, for example, SUS, aluminum, nickel, iron, titanium, and carbon can be used, and among these, aluminum or SUS is preferable.

(Electrolyte)
The nonaqueous solvent electrolyte used in combination of these positive electrode and negative electrode is generally formed by dissolving an electrolyte in a nonaqueous solvent. Examples of the non-aqueous solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, γ-butyllactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, and 1,3-dioxolane. These can be used alone or in combination of two or more. As the electrolyte, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiCl, LiBr, LiB (C ₆ H ₅ ) ₄ , or LiN (SO ₃ CF ₃ ) ₂ is used. In secondary batteries, the positive electrode layer and the negative electrode layer formed as described above are generally immersed in an electrolytic solution with a liquid-permeable separator made of nonwoven fabric or other porous material facing each other as necessary. It is formed by. As the separator, a non-woven fabric usually used for a secondary battery or a permeable separator made of another porous material can be used. Alternatively, a solid electrolyte made of a polymer gel impregnated with an electrolytic solution can be used instead of or together with the separator.

[4] Method for Producing Carbonaceous Material for Nonaqueous Electrolyte Secondary Battery Negative Electrode The method for producing a carbonaceous material for nonaqueous electrolyte secondary battery negative electrode of the present invention includes (1) an alkali metal element in plant-derived char. (2) heat-treating the alkali-derived plant-derived char at 500 ° C. to 1000 ° C. in a non-oxidizing gas atmosphere to add an alkali-treated carbonaceous precursor; A heat treatment step, (3) a vapor phase deashing step in which the alkali-treated carbonaceous precursor is heat treated at 500 ° C. to 1250 ° C. in an inert gas atmosphere containing a halogen compound, and (4) vapor phase deashing. A step of pulverizing the obtained carbonaceous precursor, (5) a step of subjecting the pulverized carbonaceous precursor to main firing at 800 ° C. to 1600 ° C. in a non-oxidizing gas atmosphere, and (6) heat treatment of the fired product. Covered with cracked carbon Capping. The method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to the present invention may further preferably include a step of (7) heat treatment at 800 ° C. to 1500 ° C. in a non-oxidizing gas atmosphere.
Although not limited, the non-aqueous electrolyte secondary battery negative electrode carbonaceous material of the present invention may be manufactured by the above-described method for manufacturing a nonaqueous electrolyte secondary battery negative electrode carbonaceous material.

<< Alkali attachment process (1) >>
The alkali-added step (1) is a step of adding an alkali-added plant-derived char by adding a compound containing an alkali metal element to the plant-derived char.

(Plant-derived char)
The plant that is the carbon source of the char derived from the plant is not particularly limited. For example, coconut shell, pea, tea leaf, sugarcane, fruit (mandarin orange or banana), persimmon, hardwood, conifer, bamboo, or Rice husk can be mentioned. These plants can be used singly or in combination of two or more kinds, but coconut shells are particularly preferable because they are available in large quantities.
The coconut as a raw material for the coconut shell is not particularly limited, and examples thereof include palm palm (oil palm), coconut palm, salak, and coconut palm. Coconut shells obtained from these palms can be used alone or in combination, but they are used as foods, detergent raw materials, biodiesel oil raw materials, etc. A shell is particularly preferred.

  In the production method of the present invention, although not limited, the aforementioned plant can be pre-fired and obtained in the form of char (for example, coconut shell char), which can be used as a raw material. preferable. Char generally refers to a carbon-rich powdery solid that is not melted and softened when coal is heated, but here it is a carbon-rich powder that is produced without heating and softening organic matter. It also refers to a solid in the form of a solid.

  Although the method to manufacture char from a plant is not specifically limited, For example, it manufactures by pre-baking a plant raw material at 300 to 550 degreeC by inert atmosphere. The pre-baking temperature is preferably 350 to 500 ° C, more preferably 375 to 450 ° C. By performing preliminary firing, a turbulent layer structure of the obtained carbonaceous material develops, and excellent press resistance can be exhibited. That is, the structure of the carbonaceous material is less likely to be destroyed with respect to the pressure at the time of manufacturing the carbon electrode (positive electrode). Therefore, by using the carbonaceous material of the present invention, excellent discharge capacity and excellent initial efficiency can be obtained.

The average particle size of the plant-derived char is not limited, but the upper limit of the average particle size is preferably 300 μm or less, more preferably 280 μm or less, and even more preferably 250 μm or less. If the average particle size is too large, the alkali metal element or alkali metal compound may be non-uniformly applied.
Further, the lower limit of the average particle diameter of the plant-derived char is not particularly limited, but is preferably 1 μm or more, more preferably 3 μm or more, and further preferably 5 μm or more. If the particle size is too small, it is difficult to separate the vapor phase containing removed potassium and the like from the plant-derived char in the vapor phase decalcification step (3).
The plant-derived char does not have to be pulverized, but can be pulverized in order to obtain the appropriate average particle size. The pulverizer used for pulverization is not particularly limited, and for example, a jet mill, a rod mill, a vibration ball mill, or a hammer mill can be used.

(Alkali metal elements or compounds containing alkali metal elements)
As the alkali metal element attached to the plant-derived char, an alkali metal element such as lithium, sodium, or potassium can be used. Lithium compounds have a problem that the effect of expanding the space is low compared to other alkali metal compounds, and the amount of reserves is small compared to other alkali metal elements. On the other hand, potassium compounds produce metal potassium when heat-treated in a reducing atmosphere in the presence of carbon, but metal potassium is more reactive with moisture than other alkali metal elements and is particularly dangerous. There is. However, in the present invention, the metal potassium is sufficiently removed because the vapor phase decalcification step (3) is performed. Therefore, metal potassium can also be used suitably. From such a viewpoint, potassium or sodium is preferable as the alkali metal element.
The alkali metal element may be attached to the plant-derived char in a metal state, but a compound containing an alkali metal element such as a hydroxide, carbonate, hydrogen carbonate, or halogen compound (hereinafter referred to as an alkali metal compound). May be attached). The alkali metal compound is not limited, but is preferably a hydroxide because it has high permeability and can be uniformly impregnated into plant-derived char.

(Char derived from alkali-attached plants)
An alkali-impregnated plant-derived char can be obtained by adding an alkali metal element or an alkali metal compound to the plant-derived char. The addition method of an alkali metal element or an alkali metal compound is not limited. For example, a predetermined amount of alkali metal element or alkali metal compound may be mixed in powder form with plant-derived char. Moreover, an alkali metal compound is dissolved in an appropriate solvent to prepare an alkali metal compound solution. After this alkali metal compound solution is mixed with plant-derived char, the solvent may be volatilized to prepare plant-derived char to which an alkali metal compound is attached. Specifically, although not limited, an alkali metal hydroxide such as sodium hydroxide is dissolved in water as a good solvent to form an aqueous solution, which is then added to the plant-derived char. After heating to 50 ° C. or higher, the alkali metal element or the alkali metal compound can be added to the plant-derived char by removing water at normal pressure or reduced pressure. Plant-derived char is often hydrophobic, and when the aqueous alkaline solution has low affinity, the affinity of the aqueous alkaline solution for the plant-derived char can be improved by adding an alcohol as appropriate. . When alkali hydroxide is used, when it is applied in the air, the alkali hydroxide absorbs carbon dioxide, and the alkali hydroxide changes to alkali carbonate. Therefore, it is preferable to reduce the carbon dioxide concentration in the atmosphere. The removal of water may be performed as long as the water is removed to such an extent that the fluidity of the alkali-derived plant-derived char can be maintained.

The amount of alkali metal element or alkali metal compound attached to the plant-derived char is not particularly limited, but the upper limit of the amount added is preferably 40.0% by weight or less, more preferably 30. It is 0 weight% or less, More preferably, it is 25.0 weight% or less. If the amount of alkali metal element or alkali metal compound added is too large, the specific surface area increases, thereby increasing the irreversible capacity. Moreover, there may be too many voids and press resistance may be reduced. The lower limit of the addition amount is not particularly limited, but is preferably 3.0% by weight or more, more preferably 5.0% by weight or more, and still more preferably 7.0% by weight or more. If the amount of alkali metal element or alkali metal compound added is too small, it is difficult to form a pore structure for doping and dedoping, which is not preferable.
When an alkali metal element or an alkali metal compound is dissolved or dispersed in an aqueous solution or an appropriate solvent, and adhering to a plant-derived char, the solvent such as water is volatilized and dried. May become solid. When heat-treating solid alkali-impregnated plant-derived char, the decomposition gas generated during the heat treatment cannot be sufficiently released, which adversely affects performance. Therefore, when the alkali-added carbonaceous precursor becomes a solid, it is preferable to crush the alkali-added plant-derived char and perform the heat treatment step (2).

<< Heat treatment process (2) >>
The heat treatment step is a step of obtaining an alkali-treated carbonaceous precursor by heat-treating the alkali-impregnated plant-derived char at 500 ° C. to 1000 ° C. in a non-oxidizing gas atmosphere.

  A suitable pore structure is formed by heat-treating the alkali-derived plant-derived char at 500 ° C. to 1000 ° C. in a non-oxidizing gas atmosphere. The temperature of heat processing is 500 to 1000 degreeC, More preferably, it is 600 to 900 degreeC, More preferably, it is 700 to 850 degreeC.

The heat treatment is performed in a non-oxidizing gas atmosphere, and examples of the non-oxidizing gas include helium, nitrogen, and argon. Moreover, heat processing can also be performed under reduced pressure, for example, can be performed at 10 kPa or less. Although the time of heat processing is not specifically limited, For example, it can carry out in 0.5 to 10 hours, and 1 to 5 hours is more preferable.
The plant-derived char has voids derived from the conduit and phloem, so the optimum pore structure is formed by the heat treatment after alkali addition, and it has excellent discharge capacity and excellent charge / discharge efficiency Can be used as a negative electrode material for secondary batteries.

<< Gas phase decalcification process (3) >>
The gas phase deashing step (3) is a step of heat-treating the alkali-treated carbonaceous precursor at 500 ° C. to 1250 ° C. in an inert gas atmosphere containing a halogen compound.

  Among the alkali metals alkali-added by the vapor phase decalcification step (3), the alkali metals remaining in the heat treatment step can be removed. Moreover, the potassium element, iron element, etc. which are contained in a plant can be removed efficiently. Furthermore, other alkali metals, alkaline earth metals, and transition metals such as copper and nickel can be removed.

Moreover, since the carbonaceous material for negative electrodes manufactured from plant-derived char can be doped with a large amount of active material, it is useful as a negative electrode material for non-aqueous electrolyte secondary batteries. However, plant-derived char contains many metal elements, and particularly contains a lot of potassium (for example, about 0.3% for coconut shell char). Carbonaceous materials produced from plant-derived char containing a large amount of metal elements such as iron (for example, coconut shell char, about 0.1% of iron element) are electrochemical when used as a negative electrode. Adverse effects on safety properties and safety. Therefore, it is preferable to reduce the content of potassium element, iron element, etc. contained in the carbonaceous material for negative electrode as much as possible. Furthermore, plant-derived char contains alkali metals (for example, sodium), alkaline earth metals (for example, magnesium or calcium), transition metals (for example, iron and copper) and other elements in addition to potassium. The content of these metals is also preferably reduced. This is because if these metals are contained, the impurities are eluted into the electrolyte during dedoping from the negative electrode, and there is a high possibility that the battery performance and safety will be adversely affected.
By the vapor phase demineralization step (3), the potassium element and the iron element contained in the plant-derived char can be efficiently removed. Further, other alkali metals, alkaline earth metals, and transition metals such as copper and nickel can be removed.

The halogen compound used for vapor phase deashing is not particularly limited, and examples thereof include fluorine, chlorine, bromine, iodine, hydrogen fluoride, hydrogen chloride, hydrogen bromide, iodine bromide, chlorine fluoride (ClF), Examples thereof include iodine chloride (ICl), iodine bromide (IBr), bromine chloride (BrCl) and the like, or compounds that generate these halogen compounds by thermal decomposition, or mixtures thereof, preferably hydrogen chloride. .
Furthermore, the halogen compound may be used by mixing with an inert gas, and the inert gas to be mixed is not particularly limited as long as it does not react with the carbonaceous material at the processing temperature, For example, nitrogen, helium, argon, krypton, or a mixed gas thereof can be mentioned, and nitrogen is preferred.
In the gas phase deashing, the mixing ratio of the inert gas and the halogen compound is not limited as long as sufficient deashing is achieved, but the amount of the halogen compound with respect to the inert gas is preferably 0. 0.05 to 10.0% by volume, more preferably 0.1 to 5.0% by volume, and still more preferably 0.2 to 3.0% by volume.

The temperature of the vapor phase decalcification is 500 ° C to 1250 ° C, preferably 600 ° C to 1100 ° C, more preferably 700 ° C to 1000 ° C, and still more preferably 800 ° C to 950 ° C. If it is less than 500 degreeC, deashing efficiency will fall and deashing may not be enough, and when it exceeds 1250 degreeC, activation by a halogen compound may occur.
The time for vapor phase decalcification is not particularly limited, but is preferably 5 minutes to 300 minutes, more preferably 10 minutes to 200 minutes, and further preferably 20 minutes to 150 minutes.
As for the temperature and time of vapor phase deashing, deashing proceeds as the temperature increases, and deashing proceeds as the time increases. Therefore, it is preferable to perform vapor phase deashing at a temperature and time such that the potassium content is 0.1% by weight or less.

  One object of the vapor phase demineralization step (3) in the present invention is a step for removing potassium and iron contained in plant-derived char. The potassium content after the vapor phase decalcification step (3) is preferably 0.10% by weight or less, more preferably 0.05% by weight or less, and further preferably 0.03% by weight or less. When the potassium content exceeds 0.10% by weight, in the obtained nonaqueous electrolyte secondary battery using the carbonaceous material for negative electrode, not only the dedoping capacity is decreased, but the undoping capacity is increased. This is because when these metal elements are eluted into the electrolytic solution and re-deposited, they cause a short circuit and may cause a serious problem in safety.

  The mechanism by which potassium, other alkali metals, alkaline earth metals, transition metals, and the like can be efficiently removed by vapor phase deashing in the production method of the present invention is not clear, but is considered as follows. A metal such as potassium contained in plant-derived char diffuses a halogen compound into an organic substance, and becomes, for example, chloride or bromide in the organic substance. And it is thought that the produced | generated chloride or bromide volatilizes (dissipates) by heating, and can decalcify potassium, iron, etc. here. Although it is considered that potassium and iron can be efficiently removed by such a mechanism as compared with liquid phase demineralization, the present invention is not limited to the above description.

  The apparatus used for the vapor phase demineralization is not limited as long as it can be heated while mixing the plant-derived char and the mixed gas of the inert gas and the halogen compound. For example, a fluidized bed using a fluidized bed is used. It can be carried out by a continuous or batch type in-layer flow system. The supply amount (circulation amount) of the mixed gas is not limited, but is 1 mL / min or more, preferably 5 mL / min or more, more preferably 10 mL / min or more per 1 g of plant-derived char.

  In vapor phase deashing, after heat treatment in an inert gas atmosphere containing a halogen compound (hereinafter sometimes referred to as “halogen heat treatment”), heat treatment in the absence of a halogen compound (hereinafter referred to as “halogen-free”). It may be preferable to carry out (sometimes referred to as “existing heat treatment”). Since the halogen is contained in the carbon precursor by the halogen heat treatment, it is preferable to remove the halogen contained in the carbon precursor by the halogen-free heat treatment. Specifically, the halogen-free heat treatment is performed by heat treatment at 500 ° C. to 1250 ° C. in an inert gas atmosphere not containing a halogen compound, and the temperature of the heat treatment is the same as the temperature of the first heat treatment, or It is preferable to carry out at a higher temperature. For example, after the halogen heat treatment, the halogen can be removed by shutting off the supply of the halogen compound and performing the heat treatment. The time for the heat treatment without a halogen is not particularly limited, but is preferably 5 minutes to 300 minutes, more preferably 10 minutes to 200 minutes, and still more preferably 10 minutes to 100 minutes.

<< Crushing process (4) >>
The pulverization step (4) is a step of pulverizing the carbonaceous precursor obtained by vapor phase decalcification. Specifically, the carbonaceous precursor is pulverized so that the average particle size is 1 to 50 μm. The pulverization can be performed after carbonization (after the main calcination). However, since the carbon precursor becomes hard as the carbonization reaction proceeds, it becomes difficult to control the particle size distribution by pulverization. After the phase decalcification step, preferably before the main calcination. The pulverizer used for pulverization is not particularly limited, and for example, a jet mill, a rod mill, a vibrating ball mill, or a hammer mill can be used. A jet mill equipped with a classifier is preferable.

<< Main firing step (5) >>
The main firing step (5) is a step of subjecting the pulverized carbonaceous precursor to main firing at 800 ° C. to 1600 ° C. in a non-oxidizing gas atmosphere. The main baking step (5) in the production method of the present invention can be performed according to a normal main baking procedure. The temperature of the main baking is 800 to 1500 ° C. The lower limit of the main calcination temperature of the present invention is 800 ° C. or higher, more preferably 1000 ° C., still more preferably 1100 ° C. or higher, and particularly preferably 1150 ° C. or higher. If the heat treatment temperature is too low, carbonization is insufficient and the irreversible capacity may increase. Further, the alkali metal can be volatilized and removed from the carbonaceous material by increasing the heat treatment temperature. That is, many functional groups remain in the carbonaceous material and the value of H / C increases, and the irreversible capacity may increase due to reaction with lithium. On the other hand, the upper limit of the main calcination temperature of the present invention is 1500 ° C. or less, more preferably 1400 ° C. or less, and particularly preferably 1300 ° C. or less. When the main firing temperature exceeds 1500 ° C., voids formed as lithium storage sites may decrease, and doping and dedoping capacity may decrease. That is, the selective orientation of the carbon hexagonal plane is increased and the discharge capacity may be reduced.

  The main firing is preferably performed in a non-oxidizing gas atmosphere. Examples of the non-oxidizing gas include helium, nitrogen, and argon, and these can be used alone or in combination. Furthermore, the main calcination can be performed in a gas atmosphere in which a halogen gas such as chlorine is mixed with the non-oxidizing gas. Moreover, this baking can also be performed under reduced pressure, for example, can also be performed at 10 kPa or less. Although the time of this baking is not specifically limited, For example, it can carry out in 0.05 to 10 hours, 0.05 to 8 hours are preferable and 0.05 to 6 hours are more preferable.

<< Coating process (6) >>
The coating step (6) is a step of coating the fired product with pyrolytic carbon. The CVD method can be used for coating with pyrolytic carbon. Specifically, the fired product is brought into contact with a linear or cyclic hydrocarbon gas, and carbon purified by thermal decomposition is deposited on the fired product. This method is well known as a so-called chemical vapor deposition method (CVD method). The specific surface area of the obtained carbonaceous material can be controlled by the coating process with pyrolytic carbon.
The pyrolytic carbon used in the present invention is not limited as long as it can be added as a hydrocarbon gas and can reduce the specific surface area of the carbonaceous material. The hydrocarbon gas is preferably mixed with a non-oxidizing gas and brought into contact with the carbonaceous material.

Although carbon number of hydrocarbon gas is not limited, Preferably it is C1-C25, More preferably, it is 1-20, More preferably, it is 1-15, Most preferably, it is 1-10. It is.
The carbon source of the hydrocarbon gas is not limited, for example, methane, ethane, propane, butane, pentane, hexane, octane, nonane, decane, ethylene, propylene, butene, pentene, hexene, acetylene, cyclopentane, cyclohexane , Cycloheptane, cyclooctane, cyclononane, cyclopropene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, decalin, norbornene, methylcyclohexane, norbornadiene, benzene, toluene, xylene, mesitylene, cumene, butylbenzene or styrene. Further, as the carbon source of the hydrocarbon gas, it is possible to use a hydrocarbon gas generated by heating a gaseous organic material and a solid or liquid organic material.

  Further, as a carbon source for pyrolytic carbon to be coated, a volatile organic compound that is solid at room temperature when the residual carbon ratio is less than 5% by weight when ignited at 800 ° C. can be used. The carbonaceous material can be coated with pyrolytic carbon by mixing the volatile organic compound with a carbonaceous material and heat-treating it in the presence of a non-oxidizing gas.

In the present invention, the volatile organic compound that can be used is a volatile organic compound that is solid at room temperature (hereinafter referred to as a volatile organic compound) having a residual carbon ratio of less than 5% by weight when incinerated at 800 ° C. Volatile substances (volatile organic substances) that can reduce the specific surface area of carbonaceous materials produced from plant-derived char (for example, hydrocarbon gases and tars) are generated. Those to be made are preferable. In the volatile organic compound used in the present invention, the content of the volatile substance (for example, hydrocarbon gas or tar component) that can reduce the specific surface area is not particularly limited, but the lower limit is 95% by weight or more. Is preferable, and the upper limit is not particularly limited. In addition, in this specification, normal temperature refers to 25 degreeC.
Examples of volatile organic substances include thermoplastic resins and low molecular weight organic compounds. More specifically, examples of thermoplastic resins include polystyrene, polyethylene, polypropylene, poly (meth) acrylic acid, poly (meth) acrylic acid ester, and the like. Examples of the low molecular weight organic compound include naphthalene, phenanthrene, anthracene, and pyrene. In the present specification, poly (meth) acrylic acid means polyacrylic acid, polymethacrylic acid, or a mixture thereof. Moreover, in this specification, poly (meth) acrylic acid ester means polyacrylic acid ester, polymethacrylic acid ester, or a mixture thereof.
In the present specification, the residual carbon ratio is measured by quantifying the amount of carbon remaining after ignition of the sample in an inert gas. The strong heat is obtained by putting approximately 1 g of volatile organic substances (this exact weight is W ₁ (g)) into a crucible and flowing the crucible in an electric furnace at 10 ° C./min. The temperature is raised to 0 ° C. and then ignited at 800 ° C. for 1 hour. The residue at this time is regarded as an ignition residue, and its weight is defined as W ₂ (g).
Next, the ignition residue is subjected to elemental analysis in accordance with the method defined in JIS M8819, and the carbon weight ratio P ₁ (%) is measured. The remaining coal rate P ₂ (%) is calculated by the following equation.

  The amount of the carbonaceous material mixed with the volatile organic compound is not limited as long as the effect of the present invention is obtained. For example, the addition amount of the volatile organic substance with respect to 100 parts by weight of the carbonaceous material is preferably 3 parts by weight or more, more preferably 5 parts by weight or more, and further preferably 7 parts by weight or more. The upper limit of the amount of the volatile organic substance added to 100 parts by weight of the carbonaceous material is not particularly limited, but is preferably 1000 parts by weight or less.

Although the temperature of a contact or heat processing is not limited, 600-1000 degreeC is preferable, 650-1000 degreeC is more preferable, 700-950 degreeC is still more preferable. Although the time of contact or heat processing is not specifically limited, For example, Preferably it is 10 minutes-5.0 hours, More preferably, it can carry out in 15 minutes-3 hours. However, the preferred contact or heat treatment time varies depending on the carbonaceous material to be coated, and basically the specific surface area of the resulting carbonaceous material can be reduced as the contact time increases. That is, it is preferable to perform the coating step under the condition that the specific surface area of the obtained carbonaceous material is 30 m ² / g or less.
Also, the apparatus used for coating is not limited, but for example, using a fluidized furnace, it can be carried out in a continuous or batch-type in-layer flow system using a fluidized bed or the like. The gas supply amount (circulation amount) is not limited.
Nitrogen or argon can be used as the non-oxidizing gas. The amount of the hydrocarbon gas added to the non-oxidizing gas is, for example, preferably 0.1 to 50% by volume, more preferably 0.5 to 25% by volume, and still more preferably 1 to 15% by volume.

<< Main firing step (5) and coating step (6) Implementation in one step>
By using the volatile organic compound, the main baking step (5) and the covering step (6) can be performed in one step. Specifically, the pulverized carbonaceous precursor and the volatile organic compound are mixed and subjected to main baking at 800 ° C. to 1600 ° C. in a non-oxidizing gas atmosphere, whereby the main baking step (5) and the coating step. (6) can be carried out in one step.
The main baking step (5) and the coating step (6) When the step is carried out in one step, the volatile organic compound is used, and the carbonaceous precursor and the volatile organic compound are mixed at the above ratio. The carbonaceous material of the present invention can be obtained by firing the obtained mixture under the firing conditions of the main firing step (5).

<< Reheat treatment process (7) >>
The production method of the present invention can preferably include a reheat treatment step (7). This reheat treatment step is a step for carbonizing the pyrolytic carbon coated on the surface by the coating step (6). In the reheat treatment step (7), heat treatment is performed at 800 ° C. to 1500 ° C. in a non-oxidizing gas atmosphere. The lower limit of the temperature of the reheating process is 800 ° C. or higher, more preferably 1000 ° C. or higher, still more preferably 1100 ° C., and particularly preferably 1150 ° C. or higher. The upper limit of the temperature of the reheat treatment step is 1500 ° C. or less, more preferably 1400 ° C. or less, and particularly preferably 1300 ° C. or less.

  The reheat treatment step is preferably performed in a non-oxidizing gas atmosphere. Examples of the non-oxidizing gas include helium, nitrogen, and argon, and these can be used alone or in combination. Furthermore, the main calcination can be performed in a gas atmosphere in which a halogen gas such as chlorine is mixed with the non-oxidizing gas. Further, the reheat treatment can be performed under reduced pressure, for example, 10 kPa or less. The time for the reheat treatment is not particularly limited, but can be performed, for example, in 0.1 to 10 hours, preferably 0.3 to 8 hours, and more preferably 0.4 to 6 hours.

EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but these do not limit the scope of the present invention.
The physical properties of the carbonaceous material (“hydrogen / carbon atomic ratio (H / C)”, “potassium content”, “helium true density”, “butanol true density”, “average particle diameter”, “ The specific surface area "," press specific surface area ratio "," NMR spectrum of lithium nuclei ") and the negative electrode" electrode density "are described in this specification, including examples. These physical property values are based on values obtained by the following method.

<< Atomic ratio of hydrogen atom to carbon atom (H / C) >>
Measurement was performed in accordance with the method defined in JIS M8819. From the mass ratio of hydrogen and carbon in the sample obtained by elemental analysis with a CHN analyzer, the hydrogen / carbon atom number ratio was obtained.

<Potassium content>
In order to measure the potassium element content, a carbon sample containing a predetermined potassium element was prepared in advance, and a calibration curve relating to the relationship with the intensity of potassium Kα ray was prepared using a fluorescent X-ray analyzer. Next, the intensity of potassium Kα ray in the fluorescent X-ray analysis was measured for the sample, and the potassium content was determined from the calibration curve prepared earlier.
The fluorescent X-ray analysis was performed under the following conditions using LAB CENTER XRF-1700 manufactured by Shimadzu Corporation. Using the upper irradiation system holder, the sample measurement area was within the circumference of 20 mm in diameter. The sample to be measured was placed by placing 0.5 g of the sample to be measured in a polyethylene container having an inner diameter of 25 mm, pressing the back with a plankton net, and covering the measurement surface with a polypropylene film for measurement. The X-ray source was set to 40 kV and 60 mA. For potassium, LiF (200) was used for the spectroscopic crystal, and a gas flow proportional coefficient tube was used for the detector, and 2θ was measured in the range of 90 to 140 ° at a scanning speed of 8 ° / min. For iron, LiF (200) was used for the spectroscopic crystal, and a scintillation counter was used for the detector, and 2θ was measured in the range of 56 to 60 ° at a scanning speed of 8 ° / min.

《Helium true density》
The measurement of the true density ρ _He using helium as a substitution medium was performed after the sample was vacuum-dried at 200 ° C. for 12 hours using a multi-volume pycnometer (Accumic 1330) manufactured by Micromeritics. The ambient temperature during measurement was constant at 25 ° C. The pressures in this measurement method are all gauge pressures and are the pressures obtained by subtracting the ambient pressure from the absolute pressure.
A multi-volume pycnometer manufactured by Micromerix, Inc. has a sample chamber and an expansion chamber, and the sample chamber has a pressure gauge for measuring the pressure in the chamber. The sample chamber and the expansion chamber are connected by a connecting pipe having a valve. A helium gas introduction pipe having a stop valve is connected to the sample chamber, and a helium gas distribution pipe having a stop valve is connected to the expansion chamber.
The measurement was performed as follows. The volume of the sample chamber (V _CELL ) and the volume of the expansion chamber (V _EXP ) were measured in advance using a standard sphere. A sample was put into the sample chamber, and helium gas was passed through the helium gas inlet tube, the connecting tube in the sample chamber, and the helium gas discharge tube in the expansion chamber for 2 hours to replace the inside of the apparatus with helium gas. Next, the valve between the sample chamber and the expansion chamber and the valve of the helium gas discharge pipe from the expansion chamber are closed (helium gas having the same pressure as the ambient pressure remains in the expansion chamber), and helium is introduced from the helium gas introduction tube of the sample chamber. After introducing the gas to 134 kPa, the stop valve of the helium gas introduction pipe was closed. The pressure (P ₁ ) in the sample chamber was measured 5 minutes after closing the stop valve. Next, the valve between the sample chamber and the expansion chamber was opened, and helium gas was transferred to the expansion chamber, and the pressure (P ₂ ) at that time was measured.
The volume of the sample (VSAMP) was calculated by the following formula.
V _SAMP = V _CELL −V _EXP / [(P ₁ / P ₂ ) −1]
Therefore, if the weight of the sample is W _SAMP , the true helium density is ρ _He = W _SAMP / V _SAMP .
The equilibrium speed was set to 0.010 psig / min.

（ここでｄは水の３０℃における比重（０．９９４６）である。）《Butanol true density》
In accordance with the method defined in JIS R7212, measurement was performed using butanol. The outline is described below. Note that both the carbonaceous precursor and the carbonaceous material were measured by the same measurement method. The mass (m ₁ ) of a specific gravity bottle with a side tube having an internal volume of about 40 mL is accurately measured. Next, the sample is put flat on the bottom so as to have a thickness of about 10 mm, and then its mass (m ₂ ) is accurately measured. Gently add 1-butanol to this to a depth of about 20 mm from the bottom. Next, light vibration is applied to the specific gravity bottle, and it is confirmed that large bubbles are not generated. Then, the bottle is placed in a vacuum desiccator and gradually evacuated to 2.0 to 2.7 kPa. Keep at that pressure for 20 minutes or more, take out after bubble generation stops, fill with 1-butanol, plug and immerse in a constant temperature water bath (adjusted to 30 ± 0.03 ° C) for 15 minutes or more. Align the liquid level of 1-butanol with the marked line. Next, this is taken out, the outside is well wiped off and cooled to room temperature, and then the mass (m ₄ ) is accurately measured. Next, the same specific gravity bottle is filled with only 1-butanol, immersed in a constant temperature water bath in the same manner as described above, and after aligning the marked lines, the mass (m ₃ ) is measured. Moreover, distilled water excluding the gas that has been boiled and dissolved immediately before use is placed in a specific gravity bottle, immersed in a constant temperature water bath as before, and the mass (m ₅ ) is measured after aligning the marked lines. The true density (ρ _Bt ) is calculated by the following formula.

(Where d is the specific gravity of water at 30 ° C. (0.9946))

《Average particle size》
Three drops of a dispersing agent (cationic surfactant “SN Wet 366” (manufactured by San Nopco)) are added to about 0.1 g of the sample, and the sample is made to conform to the dispersing agent. Next, after adding 30 mL of pure water and dispersing for about 2 minutes with an ultrasonic cleaner, the particle size was measured with a particle size distribution measuring device (“Microtrac MT3300EXII” manufactured by Microtrac Bell Co., Ltd.) with a particle size of 0.02 to 2000 μm. A range of particle size distributions was determined.
From the obtained particle size distribution, the average particle size D _v50 (μm) was _{defined as the} particle size with a cumulative volume of 50%.

を用いて液体窒素温度における、窒素吸着による１点法（相対圧力ｘ＝０．２）によりｖ_ｍを求め、次式により試料の比表面積を計算した：比表面積＝４．３５×ｖ_ｍ（ｍ^２／ｇ）（ここで、ｖ_ｍは試料表面に単分子層を形成するに必要な吸着量（ｃｍ^３／ｇ）、ｖは実測される吸着量（ｃｍ^３／ｇ）、ｘは相対圧力である。）
具体的には、カンタクローム・インスツルメンツ・ジャパン社製「ＭＯＮＯＳＯＲＢ」を用いて、以下のようにして液体窒素温度における炭素質物質への窒素の吸着量を測定した。
炭素材料を試料管に充填し、窒素ガスを２０モル％濃度で含有するヘリウムガスを流しながら、試料管を−１９６℃に冷却し、炭素材に窒素を吸着させる。次に試験管を室温に戻す。このとき試料から脱離してくる窒素量を熱伝導度型検出器で測定し、吸着ガス量ｖとした。"Specific surface area"
The specific surface area was measured according to the method defined in JIS Z8830. The outline is described below.
Approximate formula derived from BET formula

Was used to calculate v _m by the one-point method by nitrogen adsorption (relative pressure x = 0.2) at liquid nitrogen temperature, and the specific surface area of the sample was calculated by the following formula: specific surface area = 4.35 × v _m ( m ² / g) (where v _m is the amount of adsorption necessary to form a monolayer on the sample surface (cm ³ / g), v is the amount of adsorption actually measured (cm ³ / g), and x is relative Pressure.)
Specifically, the amount of nitrogen adsorbed on the carbonaceous material at the liquid nitrogen temperature was measured using “MONOSORB” manufactured by Cantachrome Instruments Japan.
The sample tube is filled with a carbon material, and the sample tube is cooled to −196 ° C. while flowing a helium gas containing nitrogen gas at a concentration of 20 mol%, and the carbon material is adsorbed with nitrogen. The test tube is then returned to room temperature. At this time, the amount of nitrogen desorbed from the sample was measured with a thermal conductivity detector, and the amount of adsorbed gas v was obtained.

《Press specific surface area ratio》
The specific surface area ratio of the press is the specific surface area (A) determined by the BET method when 0.5 g of a carbonaceous material is filled in a cylindrical mold having a diameter of 10 mm and pressed at 2.6 MPa (1 tf / cm ² ). It can be determined by the following formula from the measured specific surface area (B) before pressing.
Press specific surface area ratio = (A) / (B)
The specific surface area was measured according to the method described in the above “<< specific surface area >>”. The carbonaceous material pressed at 2.6 MPa was adjusted by filling 0.5 g of the carbonaceous material into a cylindrical mold having a diameter of 10 mm and pressing it at 2.6 MPa (1 tf / cm ² ).

<< NMR spectrum of lithium nucleus >>
N-methyl-2-pyrrolidone is added to 90 parts by weight of carbonaceous material powder and 10 parts by weight of polyvinylidene fluoride (“KF # 1100” manufactured by Kureha Co., Ltd.) to form a paste, which is uniformly applied on the copper foil, After drying, it was peeled from the copper foil to obtain a carbon electrode (positive electrode). The amount of the carbonaceous material in the positive electrode was adjusted to about 20 mg. A lithium metal thin plate having a thickness of 1 mm was used for the lithium negative electrode.
Using the obtained carbon electrode (positive electrode) and lithium negative electrode, a ratio of 1.4 mol / liter in a mixed solvent in which ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 2: 2 as an electrolytic solution. Using LiPF ₆ and a polypropylene microporous membrane as a separator to form a non-aqueous solvent type lithium secondary battery, energizing at a current density of 0.50 mA / cm ² for 1 hour and then resting for 2 hours The carbonaceous material was doped with lithium until the equilibrium potential between the terminals reached 4 mV.
After the completion of doping, the carbon electrode was taken out under an argon atmosphere for 2 hours, and the two carbon electrodes (positive electrode) (40 mg) from which the electrolytic solution had been wiped off were all filled in a sample tube for NMR measurement. In NMR analysis, MAS- ⁷ Li-NMR was measured by AVANCE-400 manufactured by BRUKER. In the measurement, LiCl was measured as a reference substance, and this was set to 0 ppm. The measurement temperature was 26 ° C.

Example 1
After adding and impregnating a sodium hydroxide (NaOH) aqueous solution in a nitrogen atmosphere to a 200 μm particle diameter coconut shell char (dry distillation at 500 ° C.), this was subjected to dehydration heating under reduced pressure to 7.0 coconut shell char. A carbonaceous precursor impregnated with NaOH by weight was obtained. Next, 10 g of the carbonaceous precursor impregnated with NaOH is heat-treated in a nitrogen atmosphere at 800 ° C., and then the nitrogen gas flowing in the reaction tube is replaced with a mixed gas of chlorine gas and nitrogen gas at 860 ° C. for 1 hour. Retained. Subsequently, the circulation of chlorine gas was stopped and kept for 30 minutes in a nitrogen atmosphere to obtain coconut shell calcined charcoal. 200 g of the obtained coconut shell pulverized charcoal was pulverized for 20 minutes by a jet mill (AIR JET MILL; MODEL 100AFG), thereby obtaining a pulverized carbonaceous precursor having an average particle size of 18 to 23 μm. The pulverized carbonaceous precursor was heated to 1200 ° C. at a temperature rising rate of 250 ° C./h and held at 1200 ° C. for 1 hour, followed by main calcination to obtain calcined charcoal. The main firing was performed in a nitrogen atmosphere with a flow rate of 10 L / min. By putting 5 g of the obtained calcined charcoal into a quartz reaction tube, heating and holding it at 780 ° C. under a nitrogen gas stream, and then replacing the nitrogen gas circulating in the reaction tube with a mixed gas of hexane and nitrogen gas The fired charcoal was coated with pyrolytic carbon. The injection rate of hexane was 0.3 g / min. After injection for 50 minutes, the supply of hexane was stopped, the gas in the reaction tube was replaced with nitrogen, and then allowed to cool to obtain a carbonaceous material 1.

Example 2
A carbonaceous material 2 was obtained in the same manner as in Example 1 except that the amount of NaOH added was changed to 15%.

Example 3
A carbonaceous material 3 was obtained in the same manner as in Example 1 except that the amount of NaOH added was changed to 18%.

Example 4
A carbonaceous material 4 was obtained in the same manner as in Example 1 except that the amount of NaOH added was changed to 20%.

Example 5
3000 g of 1% hydrochloric acid was added to 1000 g of the coffee residue after extraction, and the mixture was stirred at room temperature for 10 minutes and then filtered. Next, 3000 g of water was added, stirred for 10 minutes, and then washed with water and filtered for 3 times to perform deashing treatment to obtain a deashed coffee extraction residue. The obtained deashed coffee extraction residue was dried in a nitrogen gas atmosphere and then pre-baked at 400 ° C. to obtain a coffee char. The coffee char is crushed with a rod mill to a particle size of 20 μm, impregnated with a sodium hydroxide (NaOH) aqueous solution in a nitrogen atmosphere, and then heated and dehydrated at 120 ° C. to give 15.0 wt. A carbonaceous precursor impregnated with% NaOH was obtained. Next, 10 g of the carbonaceous precursor impregnated with NaOH is heat-treated in a nitrogen atmosphere at 800 ° C., and then the nitrogen gas flowing in the reaction tube is replaced with a mixed gas of chlorine gas and nitrogen gas at 860 ° C. for 1 hour. Retained. Subsequently, the circulation of chlorine gas was stopped and kept for 30 minutes in a nitrogen atmosphere to obtain a carbonaceous precursor. The carbonaceous precursor was heated to 1200 ° C. at a temperature rising rate of 250 ° C./h and held at 1200 ° C. for 1 hour, followed by main firing to obtain calcined charcoal. The main firing was performed in a nitrogen atmosphere with a flow rate of 10 L / min. By putting 5 g of the obtained calcined charcoal into a quartz reaction tube, heating and holding it at 780 ° C. under a nitrogen gas stream, and then replacing the nitrogen gas circulating in the reaction tube with a mixed gas of hexane and nitrogen gas The fired charcoal was coated with pyrolytic carbon. The injection rate of hexane was 0.3 g / min. After injection for 50 minutes, the supply of hexane was stopped, the gas in the reaction tube was replaced with nitrogen, and then allowed to cool to obtain a carbonaceous material 5.

Example 6
Instead of coating the pyrolytic carbon with hexane on the calcined charcoal, 5 g of the calcined charcoal and 15 g of polystyrene are mixed, 20 g of them are put into a quartz reaction tube, and the nitrogen gas flow is 780 under a flow of 0.1 L / min. A carbonaceous material 6 was obtained in the same manner as in Example 4 except that the temperature was kept at 30 ° C. for 30 minutes.

<< Comparative Example 1 >>
A carbonaceous material 7 was obtained in the same manner as in Example 1 except that the alkali deposition step was not performed.

<< Comparative Example 2 >>
A carbonaceous material 8 was obtained in the same manner as in Example 1 except that the amount of NaOH added was changed to 50%.

<< Comparative Example 3 >>
After the firing, a carbonaceous material 9 was obtained in the same manner as in Example 1 except that the coating with pyrolytic carbon was not performed.

  Using the electrodes obtained in Examples and Comparative Examples, non-aqueous electrolyte secondary batteries were prepared by the following operations (a) to (c), and the performance of the electrodes and battery performance was evaluated.

(A) Electrode preparation NMP was added to 90 parts by weight of the carbon material and 10 parts by weight of polyvinylidene fluoride (“KF # 1100” manufactured by Kureha Co., Ltd.) to form a paste, which was uniformly coated on the copper foil. After drying, it was punched out from a copper foil into a disk shape having a diameter of 15 mm and pressed to obtain an electrode. The amount of carbon material in the electrode was adjusted to about 20 mg.

(B) Production of test battery The carbon material of the present invention is suitable for constituting the negative electrode of a non-aqueous electrolyte secondary battery, but the discharge capacity (de-doping amount) and irreversible capacity (non-de-doping) of the battery active material. In order to accurately evaluate the amount) without being affected by variations in the performance of the counter electrode, a lithium secondary battery is configured using the electrode obtained above using lithium metal with stable characteristics as the counter electrode, Characteristics were evaluated.
The lithium electrode was prepared in a glove box in an Ar atmosphere. A 16 mm diameter stainless steel mesh disk is spot-welded to the outer lid of a 2016 coin-sized battery can, and then a 0.8 mm thick metal lithium sheet is punched into a 15 mm diameter disk shape. To be an electrode (counter electrode).
Using the electrode pair thus produced, the electrolyte solution was LiPF ₆ at a ratio of 1.4 mol / L in a mixed solvent in which ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 2: 2. In addition, a polyethylene gasket is used as a separator of a borosilicate glass fiber fine pore membrane having a diameter of 19 mm, and a 2016 coin-sized non-aqueous electrolyte lithium secondary battery is used in an Ar glove box. The next battery was assembled.

(C) Measurement of battery capacity About the lithium secondary battery of the said structure, the charge / discharge test was done using the charge / discharge test apparatus ("TOSCAT" by Toyo System). Lithium doping reaction on the carbon electrode was performed by the constant current constant voltage method, and dedoping reaction was performed by the constant current method. Here, in a battery using a lithium chalcogen compound as a positive electrode, the lithium doping reaction to the carbon electrode is “charging”, and in a battery using a lithium metal as the counter electrode like the test battery of the present invention, This doping reaction is referred to as “discharge”, and the naming of the lithium doping reaction to the same carbon electrode differs depending on the counter electrode used. Therefore, for the sake of convenience, the lithium doping reaction on the carbon electrode will be described as “charging”. Conversely, “discharge” is a charging reaction in a test battery, but is described as “discharge” for convenience because it is a dedoping reaction of lithium from a carbon material. The charging method employed here is a constant current constant voltage method. Specifically, constant current charging is performed at 0.50 mA / cm ² until the terminal voltage reaches 0 mV, and the terminal voltage reaches 0 mV. The constant voltage charge was performed at 0 mV, and the charge was continued until the current value reached 20 μA. At this time, the value obtained by dividing the supplied amount of electricity by the weight of the carbon material of the electrode was defined as the charge capacity (Ah / kg) per unit weight of the carbon material. After completion of charging, the battery circuit was opened for 30 minutes and then discharged. The discharge was a constant current discharge at 0.50 mA / cm ² and the final voltage was 1.5V. A value obtained by dividing the amount of electricity discharged at this time by the weight of the carbon material of the electrode is defined as a discharge capacity (Ah / kg) per unit weight of the carbon material. Furthermore, the product of the discharge capacity per unit weight and the electrode density was defined as the discharge capacity per volume (Ah / L). Moreover, the discharge capacity per weight was divided by the charge capacity per weight to determine the charge / discharge efficiency. The charge / discharge efficiency was expressed as a percentage (%).
The charge / discharge capacity and the charge / discharge efficiency were calculated by averaging the measured values of n = 3 for the test batteries prepared using the same sample.

  As shown in Tables 1 and 2, the carbonaceous materials in which the resonance peaks of Examples 1 to 6 were shifted by 110 to 160 ppm exhibited excellent discharge capacities of 522 to 585 mAh / g. Furthermore, the charging / discharging efficiency which was 86.0-88.5% was shown. On the other hand, the carbonaceous material of Comparative Example 1 having a resonance peak shifted by 100 ppm has a discharge capacity of 422 mAh / g and a charge / discharge efficiency of 83.2%, and the carbonaceous material of Comparative Example 3 having a resonance peak shifted by 92 ppm is The discharge capacity was 410 mAh / g and the charge / discharge efficiency was 65.0%. Furthermore, the carbonaceous material of Comparative Example 2 with a large amount of NaOH was not able to perform resonance peak measurement and battery performance test.

  The nonaqueous electrolyte secondary battery of the present invention has a high discharge capacity and excellent charge / discharge efficiency. Therefore, it can be effectively used for hybrid vehicles (HEV), plug-in hybrids (PHEV), and electric vehicles (EV) that require high input / output characteristics.

Claims (12)

A carbonaceous material having a plant as a carbon source, having a potassium element content of 0.10% by weight or less, a true density determined by a butanol method of 1.35 to 1.50 g / cm ³ , When the material is electrochemically doped with lithium and the NMR spectrum of the lithium nucleus is measured, it shows a main resonance peak shifted by 110 to 160 ppm on the low magnetic field side with respect to the resonance peak of LiCl as the reference material. A carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery.   The press specific surface area ratio (A / B) between the specific surface area (A) determined by the BET method when the carbonaceous material is pressed at 2.6 MPa and the specific surface area (B) before pressing is 10 or less, The carbonaceous material for a non-aqueous electrolyte secondary battery negative electrode according to claim 1.   The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to claim 1 or 2, wherein the ratio of hydrogen atoms to carbon atoms determined by elemental analysis is 0.10 or less. The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to any one of claims 1 to ³ , wherein a true density measured using helium as a substitution medium is 1.30 to 2.00 g / cm ^3. . The carbonaceous material for nonaqueous electrolyte secondary battery negative electrodes as described in any one of Claims 1-4 whose true density calculated | required by a butanol method is 1.35-1.46 g / cm < ³ >. The negative electrode for nonaqueous electrolyte secondary batteries containing the carbonaceous material of any one of Claims 1-5 . The negative electrode for a nonaqueous electrolyte secondary battery according to claim 6 , wherein the electrode density is 0.80 g / cm ³ or more. Non-aqueous electrolyte secondary battery having a negative electrode according to claim 6 or 7. (1) An alkali-adding step of adding a compound containing an alkali metal element to plant-derived char to obtain an alkali-attached plant-derived char;
(2) a heat treatment step of heat-treating the alkali-derived plant-derived char at 500 ° C. to 1000 ° C. in a non-oxidizing gas atmosphere to obtain an alkali-treated carbonaceous precursor;
(3) Gas phase deashing step in which the alkali-treated carbonaceous precursor is heat-treated at 500 ° C. to 1250 ° C. in an inert gas atmosphere containing a halogen compound (4) Carbonaceous precursor obtained by gas phase deashing Crushing process,
(5) A step of subjecting the pulverized carbonaceous precursor to main firing at 800 ° C. to 1600 ° C. in a non-oxidizing gas atmosphere, and (6) a step of coating the fired product with pyrolytic carbon.
The manufacturing method of the carbonaceous material for nonaqueous electrolyte secondary battery negative electrodes characterized by including this. When the main firing step (5) and the coating step (6) are pulverized carbonaceous precursor, and when ignited at 800 ° C., a residual volatile organic compound having a residual carbon ratio of less than 5% by weight is obtained. The manufacturing method of the carbonaceous material for nonaqueous electrolyte secondary battery negative electrodes of Claim 9 implemented by mixing and implementing this baking by 800 to 1600 degreeC by non-oxidizing gas atmosphere. (7) The method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to claim 9 or 10 , further comprising a step of heat treatment at 800 ° C to 1500 ° C in a non-oxidizing gas atmosphere. The method for producing a carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery according to any one of claims 9 to 11 , wherein the alkali-attached amount of the alkali-derived plant-derived char is 5% by weight or more.